This application is a National Stage of International Application No. PCT/SE01/0714, filed Apr. 2, 2001. This application claims the benefit of Sweden Serial No. 0001165-0, filed Mar. 31, 2000. The disclosure(s) of the above application(s) is (are) incorporated herein by reference.
The present invention relates to an apparatus for cooling electronics in accordance with the preamble of claim 1.
It is known in the art to enclose and directly cool electronics inside an outdoor cabinet by means of air taken from the environment. To this end, air drawn into the outdoor cabinet via an inlet duct, passes by the electronics to be cooled, and leaves the outdoor cabinet via an outlet duct. The electronics emit heat to the air passing by, which increases the temperature, whereby the air leaving the outdoor cabinet gets a higher temperature than the air which is drawn into the outdoor cabinet.
However, one problem arises at low environment temperatures, since electronic components can be negatively affected by temperatures below 0xc2x0 C. By providing a transverse junction having a controllable valve between the outlet duct and the inlet duct, some of or all of the heated air can be guided from the outlet duct to the inlet duct, whereby the temperature in the inlet duct may be increased, thereby avoiding damages to the electronics.
Such recirculation of air in outdoor cabinets is shown in GB 2,202,681 and U.S. Pat. No. 4,495,545. However, these valves require engines or other equipment for controlling opening and closing. This is an expensive and complicated solution.
This invention is directed to an apparatus as initially defined, and which is characterised in that a one-way valve is arranged in the outlet duct to be opened under influence of the air pressure of the heated air acting on the valve, so as to discharge air from the outlet duct. At the same time, a speed controlled fan is arranged in the transverse junction to draw air from the outlet duct, thereby controlling the amount of recirculated air to the inlet duct as well as the amount of discharged air leaving the outlet duct via the one-way valve. Hereby, recirculation of air to the inlet duct is simplified, since a passive control of the valve is possible for the opening and closing. Passive control of a valve does not require any direct mechanical engagement or engine for the opening and closing, and thereby does not require any automation and control equipment nor any energy supply from engines. Thus, a simplified way for ensuring that directly cooled electronics are maintained at a temperature above 0xc2x0 C. is provided since the air heated by the electronics is mixed with cold air in the inlet duct, so as to increase the temperature of the air which is supplied to the electronics.
Preferably, guiding ribs are provided in connection to the transverse junction. Hereby, air flowing through the transverse junction when the fan is shut off is avoided.
Suitably, a heater is provided in the inlet duct. Hereby, at low temperatures and at cold starts, heated air may be supplied to the electronics.
Advantageously, a supervisory unit is provided to detect and register temperatures in the inlet duct and the outlet duct, so as to control, in dependence of these temperatures, the number of revolutions of the fan and the supply of heat of the heater. Hereby, an optimal cooling of the electronics may be achieved.